Abstract : Milk contains high nutritive value content such as protein, carbohydrates, and minerals. In addition to all these a protein called casein is also present in it which is only found in milk ad it is valuable for human health. The microbes present in milk responsible for the spoilage and they are also destroying the nutritive value by their enzymatic activity and metabolic reactions. So it was challenging issue to overcome these problems for microbiologist and scientists for prevent the growth and entry of these hazardous microbes in the milk and their product. Bacteria like heterofermentive lactobacilli, psychotropic bacteria, gram negative bacteria, yeast, molds, other microbes produce off odour in milk which cause sour taste and are unhygienic for human consumption and results in causing different disease like typhoid, diarrhea, brucellosis, tuberculosis. For identification of such life threatening bacteria microbiologist and science technologist investigate best way to find out the main reason for the spoilage milk and milk products prepared by them through several technical and experimental methods. These methods include bacterial isolation, identification, characterization, Biochemical test, morphological identification and 16s DNA amplification of isolated bacterial colonies from milk and their products. Study showed and proved that all bacteria are not harmful for human health some bacteria are also beneficial so to restrict or destroy harmful microbes several methods and experiments are performed during the processing of milk. These process of destroying harmful microbes include pasteurization, cooling, use of antimicrobial preservatives and chemical methods. These process doesn’t make any change in milk taste and quality of milk. The main aim of this research study of these bacterial isolates for their microbial activity in milk to prevent health related issues in human and to overcome problems in their day to day life due to consumption of spoiled milk and milk products which are affected by these life threatening microbes.